Interfacing 622.08 MHz line interface to a 77.76 MHz SONET framer

Abstract

A line card for use in a node of a network to connect to optical network lines is provided. The line card includes an optical interface, and a serializer/deserializer (SERDES) operating at a first frequency. The line card also includes a framer operating at a second frequency where the first frequency is higher than the second frequency. The framer includes a digital step up converter to receive data from the SERDES and a digital step down converter to supply data to the SERDES. The step down converter includes a set of input buffers where each input buffer receives a word of nibbles from the framer. The input buffers are loaded one after another, but extraction from each of the input buffers to a multi-stage multiplexer is triggered so long as a non-reset window is preserved. The step up converter includes a set of input buffers and a register array where each input buffer receives a word of nibbles from the register array. The input buffers are loaded one after another, but extraction from the input buffers to a multi-stage multiplexer is triggered so long as a non-reset window is preserved.

1. A line card for use in a node of a network to connect to optical network lines, comprising:
 an optical interface; 
 a serializer/deserializer (SERDES) configured to operate at a first frequency; and 
 a framer configured to operate at a second frequency, the first frequency being higher than the second frequency, the framer including a digital step up converter to receive data from the SERDES and a digital step down converter to supply data to the SERDES; 
 wherein the step down converter includes a set of input buffers, each input buffer configured to receive a word of nibbles from the framer, the input buffers being loaded one after another, but extraction from each of the input buffers to a multi-stage multiplexer is triggered so long as a non-reset window is preserved; 
 wherein the step up converter includes a set of input buffers and a register array, each input buffer configured to receive a word of nibbles from the register array, the input buffers being loaded one after another, but extraction from the input buffers to a multi-stage multiplexer is triggered so long as a non-reset window is preserved, and wherein the set of input buffers of the step up converter includes 4 input buffers and the set of input buffers of the step down converter includes 4 input buffers; 
 wherein the multi-stage multiplexer of the step down converter is a 5 stage converter. 
 
     
     
       2. A line card for use in a node of a network to connect to optical network lines, comprising:
 an optical interface; 
 a serializer/deserializer (SERDES) configured to operate at a first frequency; and 
 a framer configured to operate at a second frequency, the first frequency being higher than the second frequency, the framer including a digital step up converter to receive data from the SERDES and a digital step down converter to supply data to the SERDES; 
 wherein the step down converter includes a set of input buffers, each input buffer configured to receive a word of nibbles from the framer, the input buffers being loaded one after another, but extraction front each of the input buffers to a multi-stage multiplexer is triggered so long as a non-reset window is preserved; 
 wherein the step up converter includes a set of input buffers and a register array, each input buffer configured to receive a word of nibbles from the register array, the input buffers being loaded one after another, but extraction from the input buffers to a multi-stage multiplexer is triggered so long as a non-reset window is preserved, and wherein the set of input buffers of the step up converter includes 4 input buffers and the set of input buffers of the step down converter includes 4 input buffers; 
 wherein the multi-stage multiplexer of the step up converter is a 2 stage converter. 
 
     
     
       3. A line card for use in a node of a network to connect to optical network lines, comprising:
 an optical interface; 
 a serializer/deserializer (SERDES) configured to operate at a first frequency; and 
 a framer configured to operate at a second frequency, the first frequency being higher than the second frequency, the framer including a digital step up converter to receive data from the SERDES and a digital step down converter to supply data to the SERDES; 
 wherein the step down converter includes a set of input buffers, each input buffer configured to receive a word of nibbles from the framer, the input buffers being loaded one after another, but extraction from each of the input buffers to a multi-stage multiplexer is triggered so long as a non-reset window is preserved; 
 wherein the step up converter includes a set of input buffers and a register array, each input buffer configured to receive a word of nibbles from the register array, the input buffers being loaded one after another, but extraction from the input buffers to a multi-stage multiplexer is triggered so long as a non-reset window is preserved, and wherein the set of input buffers of the step up converter includes 4 input buffers and the set of input buffers of the step down converter includes 4 input buffers; 
 wherein the register array is configured to receive 4 bit data from the SERDES and configured to send 32 bit data to the set of input buffers. 
 
     
     
       4. A line card for use in a node of a network to connect to optical network lines, comprising:
 an optical interface; 
 a serializer/deserializer (SERDES) configured to operate at a first frequency; and 
 a framer configured to operate at a second frequency, the first frequency being higher than the second frequency, the framer including a digital step up converter to receive data from the SERDES and a digital step down converter to supply data to the SERDES; 
 wherein the step down converter includes a set of input buffers, each input buffer configured to receive a word of nibbles from the framer, the input buffers being loaded one after another, but extraction from each of the input buffers to a multi-stage multiplexer is triggered so long as a non-reset window is preserved; 
 wherein the step up converter includes a set of input buffers and a register array, each input buffer configured to receive a word of nibbles from the register array, the input buffers being loaded one after another, but extraction from the input buffers to a multi-stage multiplexer is triggered so long as a non-reset window is preserved, and wherein the set of input buffers of the step up converter includes 4 input buffers and the set of input buffers of the step down converter includes 4 input buffers; 
 wherein the multi-stage multiplexer of the step down converter is configured to receive 32 bit data and to output 4 bit data. 
 
     
     
       5. A line card for use in a node of a network to connect to optical network lines, comprising:
 an optical interface; 
 a serializer/deserializer (SERDES) configured to operate at a first frequency; and 
 a framer configured to operate at a second frequency, the first frequency being higher than the second frequency, the framer including a digital step up converter to receive data from the SERDES and a digital step down converter to supply data to the SERDES; 
 wherein the step down converter includes a set of input buffers, each input buffer configured to receive a word of nibbles from the framer, the input buffers being loaded one after another, but extraction from each of the input buffers to a multi-stage multiplexer is triggered so long as a non-reset window is preserved; 
 wherein the step up converter includes a set of input buffers and a register array, each input buffer configured to receive a word of nibbles from the register array, the input buffers being loaded one after another, but extraction from the input buffers to a multi-stage multiplexer is triggered so long as a non-reset window is preserved, and wherein the set of input buffers of the step up converter includes 4 input buffers and the set of input buffers of the step down converter includes 4 input buffers; 
 wherein the multi-stage multiplexer of the step up converter is configured to receive 32 bit data and to output 4 bit data. 
 
     
     
       6. In an optical network, a framer that is connected with a serializer/deserializer (SERDES) within a line card, the framer comprising:
 a digital step down converter including,
 a multi-stage multiplexer being configured to supply data to the SERDES, 
 a set of input buffers, each input buffer configured to receive a word of nibbles from the framer, the input buffers being loaded one after another, but extraction from each of the input buffers to the multi-stage multiplexer is triggered so long as a non-reset window is preserved; and 
 
 a digital step up converter including,
 a register array being configured to receive data from the SERDES; 
 a set of input buffers, each input buffer configured to receive a word of nibbles from the register array, the input buffers being loaded one after another, but extraction from the input buffers to a multi-stage multiplexer is triggered so long as a non-reset window is preserved; 
 
 wherein the SERDES is configured to operated at a first frequency and the framer is configured to operate at a second frequency, the first frequency being higher than the second frequency, wherein the register array is configured to receive 4 bit data from the SERDES and configured to send 32 bit data to the set of input buffers. 
 
     
     
       7. A framer as recited in  claim 6 , wherein the multi-stage multiplexer of the step down converter is a 5 stage converter. 
     
     
       8. A line card for use in a node of a network to connect to optical network lines as recited in  claim 6 , wherein the multi-stage multiplexer of the step up converter is a 2 stage converter. 
     
     
       9. A line card for use in a node of a network to connect to optical network lines as recited in  claim 6 , wherein the set of input buffers of the step up converter includes 4 input buffers and the set of input buffers of the step down converter includes 4 input buffers. 
     
     
       10. A line card for use in a node of a network to connect to optical network lines as recited in  claim 6 , wherein the first frequency is 622.08 MHz. 
     
     
       11. A line card for use in a node of a network to connect to optical network lines as recited in  claim 6  wherein the second frequency is 77.76 MHz. 
     
     
       12. A line card for use in a node of a network to connect to optical network lines as recited in  claim 6 , wherein the multi-stage multiplexer of the step down converter is configured to receive 32 bit data and to output 4 bit data. 
     
     
       13. A line card for use in a node of a network to connect to optical network lines as recited in  claim 6 , wherein the multi-stage multiplexer of the step up converter is configured to receive 4 bit data and to output 32 bit data. 
     
     
       14. A line card for use in a node of a network to connect to optical network lines, comprising:
 an optical interface; 
 a serializer/deserializer (SERDES) configured to operate at a first frequency, the SERDES being connected to the optical interface; and 
 a framer configured to operate at a second frequency, the first frequency being higher than the second frequency, the framer including a digital step up converter and a digital step down converter; 
 wherein the step down converter includes a set of 4 input buffers, each input buffer configured to receive a word of nibbles from the framer, the input buffers being loaded one after another, but extraction from each of the input buffers to a 5 stage multiplexer is triggered so long as a non-reset window is preserved, the 5 stage multiplexer being configured to supply data to the SERDES; 
 wherein the step up converter includes a set of 4 input buffers and a register array, each input buffer configured to receive a word of nibbles from the register array, the input buffers being loaded one after another, but extraction from the input buffers to a 2 stage multiplexer is triggered so long as a non-reset window is preserved, and the register array of the step up converter being configured to receive data from the SERDES, wherein the register array is configured to receive 4 bit data from the SERDES and configured to send 32 bit data to the set of input buffers. 
 
     
     
       15. A line card for use in a node of a network to connect to optical network lines as recited in  claim 14 , wherein the first frequency is 622.08 MHz. 
     
     
       16. A line card for use in a node of a network to connect to optical network lines as recited in  claim 15 , wherein the second frequency is 77.76 MHz. 
     
     
       17. In an optical network, a framer that is connected with a SERDES within a line card, the framer comprising:
 a digital step down converter including,
 a five stage multiplexer being configured to supply 4 bit data to the SERDES, 
 a set of four input buffers, each input buffer configured to receive eight sets of 4 bit data from the framer, the input buffers being loaded one after another, but extraction from each of the input buffers to the five multiplexer is triggered so long as a non-reset window is preserved; and 
 
 a digital step up converter including,
 a register array being configured to receive 4 bit data from the SERDES; 
 a set of four input buffers, each input buffer configured to receive 8 sets of 4 bit data from the register array, the input buffers being loaded one after another, but extraction from the input buffers to a two stage multiplexer is triggered so long as a non-reset window is preserved; 
 
 wherein the SERDES is configured to operated at a frequency of is 622.08 MHz and the framer is configured to operate at a frequency of 77.76 MHz, and wherein the 2 stage multiplexer of the step down converter is configured to receive 32 bit data and to output 4 bit data. 
 
     
     
       18. A line card for use in a node of a network to connect to optical network lines as recited in  claim 17 , wherein the five multiplexer of the step up converter is configured to receive 4 bit data and to output 32 bit data. 
     
     
       19. A method for transferring data between a framer and a serializer/deserializer (SERDES) of a line card used in an optical network, comprising:
 when the data is being transferred from the framer to the SERDES, 
 receiving data from the framer, the framer operating at a first frequency, 
 loading the data in a set of input buffers of a digital step down converter, the input buffers being loaded one after another, each of the input buffers holding a word of nibbles, 
 extracting the data from each of the input buffers of the digital step down converter to a multi-stage multiplexer of the step down converter, the input buffers being extracted one after another, the extracting being triggered so long as a non-reset window of the step down converter is preserved, 
 transmitting the data from the multi-stage multiplexer of the step down converter to the SERDES, the SERDES configured to operate at a second frequency, the first frequency being higher than the second frequency; and 
 when the data is being transferred from the SERDES to the framer,
 transferring the data from the SERDES to a register array, 
 
 receiving the data from the register array, 
 loading the data in a set of input buffers of a digital step up convertor, the input buffers being loaded one after another, each of the input buffers holding a word of nibbles, 
 extracting the data from each of the input buffers of the digital step up converter to a multi-stage multiplexer of the step up converter, the input buffers being extracted one after another, the extracting being triggered so long as a non-reset window of the step up converter is preserved, 
 transmitting the data from the multi-stage multiplexer of the step up converter to the framer, and wherein the multi-stage multiplexer of the step down converter is a 5 stage converter. 
 
     
     
       20. A method for transferring data between a framer and a serializer/deserializer (SERDES) of a line card used in an optical network as recited in  claim 19 , wherein the multi-stage multiplexer of the step up converter is a 2 stage converter. 
     
     
       21. A method for transferring data between a framer and a serializer/deserializer (SERDES) of a line card used in an optical network as recited in  claim 20 , wherein the first frequency is 622.08 MHz and the second frequency is 77.76 MHz. 
     
     
       22. A method for transferring data between a framer and a serializer/deserializer (SERDES) of a line card used in an optical network as recited in  claim 21 , wherein the register array is configured to receive 4 bit data from the SERDES and configured to send 32 bit data to the set of input buffers. 
     
     
       23. A method for transferring data between a framer and a serializer/deserializer (SERDES) of a line card used in an optical network as recited in  claim 22 , wherein the multi-stage multiplexer of the step down converter is configured to receive 32 bit data and to output 4 bit data. 
     
     
       24. A method for transferring data between a framer and a serializer/deserializer (SERDES) of a line card used in an optical network as recited in  claim 23 , wherein the multi-stage multiplexer of the step up converter is configured to receive 32 bit data and to output 4 bit data. 
     
     
       25. A method for transferring data between a framer and a serializer/deserializer (SERDES) of a line card used in an optical network as recited in  claim 23 , wherein extracting the data from each of the input buffers of the digital step down converter to a multi-stage multiplexer of the step down converter includes,
 extracting the data from a particular one of the input buffers of the digital step down converter to a multi-stage multiplexer of the step down converter when at least one additional input buffer has been filled after the particular one of the input buffers has been filled. 
 
     
     
       26. A method for transferring data between a framer and a serializer/deserializer (SERDES) of a line card used in an optical network as recited in  claim 23 , wherein extracting the data from each of the input buffers of the digital step up converter to a multi-stage multiplexer of the step up converter includes,
 extracting the data from a particular one of the input buffers of the digital step up converter to a multi-stage multiplexer of the step up converter when at least one additional input buffer has been filled after the particular one of the input buffers has been filled.